The present invention relates generally to fluid level monitoring and, more particularly, to a method and apparatus for remote monitoring of the level of a liquid in a closed container.
Liquid level monitoring is important in many applications. For example, the level of fuel in the fuel tank of a vehicle or other device typically is monitored, at least periodically, to allow the user to schedule re-filling, to monitor efficiency, for cost accounting, and/or for a variety of other reasons. Similarly, the level of liquid in storage tanks or mixing tanks of various processes or systems is commonly monitored. Often, the container is closed to prevent external contamination of its contents and/or to prevent loss by spillage or evaporation. In instances wherein the container is closed, and/or if the container is located remotely from the desired monitoring location, it is desirable to provide for remote monitoring of the liquid level. Remote monitoring is often accomplished by provision of a liquid level sensor or probe within the container, and a remote gauge or other indicator at the desired monitoring location. The gauge or other indicator is typically coupled to the level sensor or probe by a mechanical linkage or electrical conductors.
One particular application in which remote monitoring is desirable is in the monitoring of fuel level within a closed liquid propane tank. Propane-powered industrial machinery of various types is in widespread use throughout the world. For example, forklifts and other propane-powered equipment are commonly used in warehouses, factories, production facilities, home stores, etc., for the movement, loading and unloading of equipment and supplies. The use of propane as a fuel for indoor machinery is desirable because of its low carbon monoxide tailpipe emissions.
Furthermore, gasoline engines originally provided on industrial machinery often are converted from gasoline to propane for indoor applications. Many gasoline-powered forklifts are originally provided with a dashboard gauge for monitoring the level of gasoline in the vehicle""s fuel tank. When a forklift is converted to propane, this gauge is typically disconnected, and a sticker placed over the gauge indicating the gauge is no longer in operation.
On a typical propane-powered forklift, a replaceable, refillable, fuel cylinder is carried on board by use of a strap-bracket assembly. Aluminum forklift propane cylinders are commercially available from a variety of sources, including Worthington Cylinder Corporation of Columbus, Ohio. Many cylinder manufacturers offer a permanent float-type gauge as part of the cylinder. These gauges include a level float or probe mounted internally of the tank, which is linked to a dial gauge affixed to the top end of the cylinder for viewing. However, because the cylinder is typically mounted behind the operator""s seat or otherwise beyond the direct line of sight of the operator during normal use, the operator seldom checks the fuel level in the tank. When the fuel level is not readily viewable, the driver will often forget to periodically check the level and will sometimes allow the engine to run out of fuel. When this happens, a full cylinder must be carried from its storage location to the forklift. Depending on where the machine stopped, this distance may be considerable, resulting in lost time and productivity.
Furthermore, when a cylinder is emptied it is usually replaced with a full cylinder, instead of storing and dispensing liquid propane on site. Because of the frequent exchange of an empty cylinder for a full one, the same cylinder practically never stays on a given piece of machinery. Therefore, the provision of an electrically-coupled or mechanically-linked fuel level monitoring system coupling the float type gauge of the cylinder to a dashboard indicator would be very inconvenient, if not impractical. Wires or linkages connecting the level sensor of the cylinder to the dashboard-mounted gauge would have to be disconnected from the empty cylinder and reconnected to the full cylinder upon each tank change.
Accordingly, it can be seen that there is a need for an improved method and apparatus for monitoring the level of a liquid in a container. A particular need exists for a level monitoring method and apparatus enabling a forklift operator to remotely monitor fuel level within a replaceable propane cylinder. A further need exists for such a method which permits observation of the monitored level at a location in or near the direct line of sight of the operator during normal operation, and which allows replacement of cylinders without the inconvenience of disconnecting and reconnecting the monitoring equipment. It is to the provision of a method and apparatus meeting these and other needs that the present invention is primarily directed.
Briefly described, the present invention comprises a method and apparatus for remote monitoring of a liquid level in a container. In an exemplary embodiment, the invention comprises a method and apparatus providing dashboard monitoring of liquid level of a DOT/ICC type propane cylinder mounted on a propane-powered machine. The machine can be a forklift or other device with an exchange-type cylinder mounted out of the driver""s view. The cylinder may or may not be provided with a liquid level float gauge readable at the cylinder.
The invention comprises the provision of a floating magnet within the propane cylinder and a series of spaced sensors mounted along the bend of the bracket-strap typically provided on the vehicle for anchoring the cylinder. The spacing of the sensors can be selected to generally coincide with proportionately spaced liquid levels of fuel within the cylinder. When the magnet moves into the vicinity of one of the sensors, a signal corresponding to the sensor is sent to a controller which in turn sends an electrical signal to the dash-mounted gauge and illuminates a corresponding level-indicating light or otherwise effects indication of the fuel level.
Considered in one aspect, the present invention is a system for remote monitoring of a level of liquid within a container. The system can include at least one magnetic float provided within the container; at least one sensor mounted to a structure external of and adjacent the container; an indicator remote from the container for indicating at least one level of liquid within the container, each indicated level corresponding to the respective sensor; and a controller or other means for processing and communicating signals from the at least one sensor to the indicator. The sensors can be provided mounted onto a flexible member so that the sensor spacing is preset and the member can be easily installed adjacent the container.
In another aspect, the present invention is an improvement to a vehicle of the type having a removable and replaceable fuel cylinder. The improvement can include a remote fuel level monitoring system including an array of sensors mounted to the vehicle adjacent the fuel cylinder for sensing proximity of a magnetic float disposed within the fuel cylinder; a fuel level indicator remote from the fuel cylinder; and a controller or other means for receiving and processing signals from the array of sensors and transmitting signals to the fuel level indicator, whereby the fuel level indicator provides an indication of the level of fuel within the cylinder, and whereby cylinders can be removed and replaced without disconnecting the remote fuel level monitoring system.
In yet another aspect, the present invention is a method for remote monitoring of a level of liquid within a container. The method can include the steps of providing at least one magnetic float within the container; providing at least one sensor mounted to a structure external of and adjacent the container; providing an indicator remote from the container for indicating at least one level of liquid within the container, each indicated level corresponding to the respective sensor; and processing and communicating signals from the at least one sensor to the indicator, thereby indicating a level of liquid within the container.
In another aspect, the invention is a method for retrofitting a pre-existing liquid level indicator to provide for remote liquid level monitoring. The method includes the steps of providing one or more magnetic proximity sensors; providing at least one controller with resistance characteristics selected to correspond to the resistance characteristics of the pre-existing indicator; connecting the sensors to the controller; and connecting the controller to the pre-existing indicator. The retrofit method can further include the step of providing a liquid container with at least one magnetic float disposed therein.
In still another aspect, the present invention can include a liquid container for use with a remote level monitoring system. The container includes a shell bounding a contained volume, at least one opening through the shell communicating with the contained volume, and a magnetic float disposed within the contained volume.
In a further aspect, the present invention is a magnetic float for use within a container forming a portion of a remote level monitoring system, the float comprising a body buoyant in liquid of the type contained in the container, at least a portion of the float comprising a magnetic material.
These and other objects, features, and advantages of the present invention will become more apparent upon reading the following description in conjunction with the accompanying drawing figures.